There exists a need for safe disposal of pyrotechnic, explosive and propellant materials without open burning or open detonation (OB/OD) and without accidental detonation during the disposal process. The volume of such materials that require disposal has greatly increased due to the reduction in inventories of weapons following the end of the Cold War. Existing processes for disposal do not fully meet the needs for Class 1.1, 1.2 and some 1.3 rocket propellants.
Class 1.1 rocket propellants create the greatest problem for disposal by other than open detonation since the nitroglycerine and nitrocellulose in the Class 1.1 propellant matrix make the composition detonatable. Class 1.2 rocket propellants, while still being detonatable, do not contain nitroglycerine and are less shock sensitive than those of Class 1.1. Class 1.3 propellants contain ammonium perchlorate (AP) rather than nitroglycerine and nitrocellulose with the rocket propellants representing primarily a fire hazard during disposal rather than an explosion hazard.
Prior to the present invention, water jets have been employed to remove propellant from a loaded rocket motor. This method has been quite effective with Class 1.3 propellants. It is also effective with 1.1 propellants but the remaining "crumb" is still detonable. In addition, a problem with the use of water jets still exists because this method produces contaminated water, thereby adding to the disposal problem.
U.S. Pat. No. 4,854,982 discloses the physical process of extracting and recovering ammonium perchlorate (AP) from a solid composite propellant composition using liquid ammonia in a pressurized recycle system. This system was run under ambient temperatures wherein ammonia was liquified under its own vapor pressure at about 114 psig. AP was recovered by precipitation in a uniform size and configuration for recycling or other uses by vaporization of liquid ammonia containing dissolved AP. By selectively dissolving out AP from the propellant the solid matrix became porous such that the other components of the composition were mechanically removed.
A problem exists with some rocket propellants which contain some AP even after the AP is dissolved out by the liquid ammonia. The porous structure which remains must still be broken up by physical means. This can be a dangerous undertaking in situations where the AP has been removed but nitroglycerine or nitrocellulose are still a part of the porous structure.
High pressure sprays of oil have been used in a manner similar to water jets to physically break up the structure of Class 1.3 propellants. This method has not been useful for crosslinked propellants, where it has been necessary to cut into the metal casing of a rocket motor in order to physically remove the propellant. The physical shock of cutting into a rocket motor casing containing Class 1.1 or 1.2 propellant may detonate or ignite the composition.
Thus prior to the present invention, a need existed for a safe and cost efficient method of disposal for Class 1.1, 1.2 and some 1.3 propellants which contained shock sensitive nitrate esters (nitroglycerine and nitrocellulose) and other detonatable ingredients.